Modares Journal of Biotechnology

Abstract Objectives: Methanotrophs are microorganisms that utilize methane as a carbon and energy source, playing a crucial role in the carbon cycle. Due to their high potential for single-cell protein (SCP) production, they are considered valuable candidates in biotechnological industries. This study aimed to investigate the enhancement of biomass production under aerobic and anaerobic methane conditions for three methanotrophic species-Methylococcus capsulatus (Bath), Methylomicrobium album BG8, and Methanoperedens nitroreducens-using in silico approach.
Materials and Methods: The genome-scale metabolic models of these microorganisms (iMcBath, iJV803, and iMN22HE) were reconstructed and analyzed using the COBRA Toolbox in the MATLAB environment. Target reactions for optimization were selected based on flux sensitivity analysis and a comprehensive literature review identifying key reactions in methane oxidation and nitrogen metabolism. Subsequently, Flux Balance Analysis (FBA) was performed to evaluate biomass flux under baseline and optimized conditions, and the results were comparatively assessed.
Results: After the applied metabolic modifications, the biomass flux of M. capsulatus, M. album, and M. nitroreducens increased by 2.28, 1.94, and 1.25-fold compared to their baseline states, respectively. Moreover, flux sensitivity and variability analyses indicated that the model predictions were robust against changes in substrate uptake rates.
Conclusion: Given the substantial increase in biomass yield of Methylococcus capsulatus (Bath), along with its established biotechnological relevance and available cultivation technology, it is recommended that the proposed metabolic modifications be experimentally validated to expand its potential industrial and bioprocess applications.

Abstract The microalgal strain Aurantiochytrium sp. shy contains considerable amounts of poly-unsaturated fatty acids (PUFAs), chiefly docosahexaenoic acid (DHA) with potential pharmaceutical and health-related attributes. Effects of various concentrations of glucose, meat extract, monosodium glutamate and sea salt on the algal biomass and DHA production have been investigated in this study. Maximum algal biomass (7.1 g/l) was obtained when the culture medium contained 60 g/l of glucose, 6 g/l of meat extract, 6 g/l monosodium glutamate and sea salt at 25ppt. Lipid contents of the alga exceeded 30% of its dry cell weight, with palmitic acid and DHA as the most abundant components. When the effect of a single additive was concerned, meat extract was significantly effective, while interaction between meat extract and glucose was the most effective in comparison with other interactions (P < 0.0001). According to the results, glucose can assure more algal and fatty acids production when adequate amounts of meat extract exist in the culture medium. Optimal results attained when the ratios of glucose to meat extract and C/N concentrations were 10 and 5, respectively. Due to its remarkable growth rate and the capability to produce substantial quantities of biomass and fatty acids, Aurantiochytrium sp.shy was found to be a major source of the beneficial ingredients, whose productivity can magnify if its culture conditions is optimized using favorable blend of growth-promoting materials.

Abstract Conventional wastewater treatment systems are not capable of removing phosphorus effectively. The entry of phosphorus into water resources leads to the formation of an Eutrophication phenomenon. One of the methods for phosphorus removal is the use of microalgae. In this way, besides helping with advanced sewage treatment, it can produce algae with many applications. The purpose of this study was to determine the simultaneous and to compare the phosphorus removal (rate of phosphorus) and Spirulina biomass production in a photobioreactor, using two kinds of treated sewage. The experiments were carried out with the manufacture of a photobioreactor and air injection by means of a fine bubble diffuser into sewage-containing reactors. The light source in this test was designed as fluorescent light bulbs and alternating radiation. Urban wastewater effluent and refined sewage were used as a culture medium in a photobioreactor. The amount of phosphorus in the purified sewage was measured by spectrophotometry at a wavelength of 690nm. The phosphorus removal and algal biomass production were measured in different culture medium containing wastewater with various concentrations of phosphorus. The initial concentrations of phosphorus in refined urban sewage and sanitary sewage were 1.96 and 0.4mg L^-1, respectively. Phosphorus removal during microalgae cultivation with municipal wastewater and sanitary sewerage (removal of phosphorus) for 8 days, was 71.9% and 37%, respectively. Biomass production in this time were 0.18 and 0.025g/l, respectively. By decreasing the concentration of phosphorus in the wastewater, the amount of biomass production and (removal of) phosphorus removal decreased. Treated domestic and sanitary sewage can be injected directly, without prior treatment, in photobioreactor and it is possible to remove phosphorus and to produce algal biomass.

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